1. Field of Invention
The invention relates to the field of real time, multiuser, time-share computer systems and specifically to multiuser personal computer systems for running computer software written for individual personal computers, including software that requires the interactive exchange of high resolution computer graphics information.
2. Description of Related Art
Software manufactures have developed a considerable number of software programs for the personal computer. The development of software packages, particularly for business applications, has been assisted immensely by the establishment of standard operating hardware that is accepted through out the industry. The large number of software packages that have been written for the personal computer and the enormous effort made to develop software for business applications combine to encourage hardware manufactures to develop computer systems that can run existing software.
Many software packages have been written to directly access specific elements of operating hardware found on the standard personal computer. Therefore, any computer must have direct access to the hardware found on the standard PC if that computer is to execute conventional software packages. Many software packages have also been written so that the computer can perform only one function at a time. These single tasking systems essentially tie down all the hardware on the PC so that multitasking at the PC is a nontrivial problem.
A new generation of the personal computer has recently been introduced by Compacq. At the most basic level, the 8088 microprocessor, used as the central processing unit (CPU) of current personal computers such as the IBM XT and AT series has been replaced with a vastly more powerful CPU, the 80386 microprocessor manufactured by Intel. The '386 CPU can execute the software packages written for the current generation of PC. The full capabilities of the '386 CPU, however, cannot be exploited by software written to run on a PC using the less powerful 8088 CPU.
The capabilities of the '386 CPU may be further exploited by running several applications programs concurrently. The '386 microprocessor has an extraordinary capability to link together a large number of remote, low cost work stations by appearing to each station as a separate CPU that is dedicated to serving that one station. This multitasking, multiuser mode of operation, however, is limited by the number of input/output ports available at the computer. It is physically impractical to place enough I/O ports in close enough proximity to the CPU to fully exploit the multiuser, multitasking capabilities of the '386 CPU, especially for executing software written for less powerful personal computers.
One way to more fully utilize the capabilities of a '386 CPU is to form a multiuser system of remote terminals that use the '386 CPU on a time-share basis. However, the use of remote terminals presents a problem for executing software that is written for the personal computer. The '386 CPU must have direct access to whatever operating hardware the software may request at the remote work station. For example, programs for such diverse applications as spread sheets and word processing require direct access to video memory for displaying high resolution graphics. Conventional software packages that have been written for a single user, single tasking personal computer are not compatible with a multiuser, time-share system of the type otherwise permitted by the '386 microprocessor because the software cannot access the operating hardware located at the remote terminal.
Various attempts have been made to link personal computers to permit multiple users to share both hardware and software. One common approach is the local area network (LAN). A LAN can provide peer to peer data communications but not centralized management and control of the type permitted by the new generation PC. Most LAN networks are expensive because each personal computer in the network requires a separate network card to interface with the network and the industry does not have an accepted standard LAN or LAN interface. Conventional LAN's, and other networking systems, transfer data between stations at a slow rate which is totally inadequate for the high resolution, interactive graphics contained numerous software packages.
The art recognizes a need for a multiuser computer system for executing application software including high resolution, interactive graphics packages in a real time, time-share system. The art also recognizes a need to economically link remote terminals with a central computer using hardware that is fully compatible with the software written for the single user, single tasking generation of personal computer.